1. Field of the Invention
This invention relates to a liquid sealed type rubber mount device such as an engine mount rubber for an automobile vehicle.
2. Description of the Prior Art
Such a liquid sealed type rubber mount device is disclosed for example in Japanese Patent Publication (Kokoku) No. Sho62-23178, in which a first support member is attached to a vibration source, a cylindrical shaped second support member is attached to a vehicle body, a conical shaped rubber body is interposed between the two support members, and a liquid chamber is formed within tie rubber body to admit buffering liquid therein, wherein a thin wall portion is partially provided on the rubber body, a disk shaped member is provided projecting from the first support member into the second support member, a partition member is arranged to divide the second support member into two chambers, while an annular passage is formed between an outer peripheral portion thereof and an inner wall of the second support member and a diaphragm is provided on a bottom portion of the second support member.
According to an above stated construction, since it is aimed to damp a vibration by a flow resistance, the device can deal with the vibration of some 10 Hz and to the contrary, it has a high dynamic spring characteristic in a frequency range for example 100 to 500 Hz and a high frequency range for example 500 to 1000 Hz.
On the other hand, it is known that the rubber wall of the liquid chamber is not provided with such a thin portion and is instead formed with a uniform thickness with respect to to a circumferential direction, and a disk shaped member, which is connected to a vibration input side projecting into the liquid chamber, whereby the low dynamic spring characteristic is realized. A curve shown as a conventional example in FIG. 3 describes a change of the dynamic spring characteristics vs. the frequency in such a construction. In such a liquid sealed type mount device, the disk shaped member acts as a medium frequency device and a minimum value a is generated by a liquid column resonance at a specified frequency in the medium frequency range accompanying a flow of liquid in a gap between the peripheral rubber wall and the disk shaped member.
However, even if the dynamic spring constant becomes low in the medium frequency range, as observed as a peak b by a reaction of the low dynamic spring constant in a little higher frequency, which result in showing the high dynamic spring constant in the high frequency range. Meanwhile, in recent years on the precondition of the low dynamic spring constant in a low frequency range, it is required that the dynamic spring characteristic is made lower not only in the medium frequency range but also in the high frequency range and the low dynamic spring characteristic is realized in a wide frequency range.